Photo: NICK COBBING / GREENPEACE
Melting ice is causing their numbers to drop dramatically, they warn.
Others also at risk include ivory gulls, Pacific walruses, ringed and hooded seals and narwhals, small whales with long, spiral tusks.
One of the problems is that other animals are moving north, encroaching on their territory, spurred by increasing temperatures, pushing out native species.
The animals are also struggling with the loss of sea ice.
"The Arctic as we know it may soon be a thing of the past," said Eric Post, associate professor of biology at Penn State University, who led the latest study, publied in the journal Science.
"Recent projections suggest polar bears could be extinct within 70 years.
"But we think this could be a very conservative estimate. The outlook is very bleak for them and other creatures such as ringed seals.”
He added: "The rate at which sea ice is disappearing is accelerating and these creatures rely on it for shelter, hunting and breeding. If this goes, so do they.”
The international team analysed average temperature in the Arctic over the last 150 years and warn many animals that are dependent upon the stability and persistence of sea ice are faring especially badly.
Polar bears and ringed seals both give birth in lairs or caves under the snow and can lose many newborn pups when the lairs collapse in unusually early spring rains, triggered by climate change.
Among animals migrating further north are red foxes, which are driving out the smaller Arctic foxes.